1. Field of The Invention
The present invention relates to heat sinks for central processing units ("CPU"). More particularly, it relates to heat sinks for "PENTIUM" CPUs used with baby AT mother boards.
2. Description of the Prior Art
As the circuitry for personal computers became more integrated, the majority of the components came to be located on a single printed circuit board--most often referred to as a mother board. A typical mother board provides the primary interconnections for the CPU and its support circuits, the memory--both RAM and ROM--the I/O interface and the system bus or busses.
The mother board typically occupies most if not all of the bottom of the computer's case. All of the other components of the computer occupy the space above the mother board. At the front of the case are the disk drives, which are the only mechanical components in the system. These devices use more power than most other components and therefore connect directly to the power supply. Various peripherals and peripheral expansion bays occupy some of the space above the mother board. The remaining space is reserved for expansion boards. The remaining space is reserved for expansion boards.
While the majority of a computer's components are attached directly to the mother board, there are many occasions in which it is desirable to connect other devices to the mother board. To accommodate this need, most modern mother boards have connectors mounted on the mother board into which expansion boards may be plugged. The connectors are connected to the bus on the mother board. Expansion boards are positioned perpendicular to the mother board. Expansion boards attached to computers in this way are housed in a rigid mechanical structure called a card cage which mechanically stabilizes the expansion board and helps to provide air circulation to keep the electrical components cool.
One of the characteristics of the personal computer industry is that it involves a vast number of independent suppliers of system components. In order for this industry organization to work effectively, rigorous standards must be established for how the components of the system will interface with each other. This applies to mother boards and all of the components that plug into the mother board. Its size and layout are specified.
Currently one of the most extensively used mother boards is referred to as the baby AT mother board. A typical personal computer chassis showing the location of a baby AT mother board is set out in FIG. 1. Referring now to FIG. 1, a bottom member 10 of a typical personal computer chassis has located thereon a power supply 12 as well as spaces 14 and 15 for various disk drives and disk drive expansion space. There is also a fan, not shown, for supplying a flow of air across the various components to keep them below a specified temperature. A mother board 17 is attached to bottom member 10 A CPU assembly 18 is mechanically and electrically attached to mother board 17. CPU assembly 18 typically consists of a socket mounted to mother board 17, a packaged CPU chip inserted into the socket and in some cases a heat sink mounted on top of the packaged CPU chip. Additional mother board components such as memory and CPU support chips are located in area 20. Expansion board connectors 21 through 28 are also mechanically and electrically connected to mother board 17. Significantly, the clearance between the baby AT mother board and the closest edge of an expansion board is specified at 0.6 inches. This standard cannot be economically changed.
The "PENTIUM" CPU manufactured by Intel Corporation is a high performance CPU operating at frequencies from 60 to 133 MHz. As a result, the "PENTIUM" dissipates considerable heat. In order to keep the "PENTIUM" within its specified operating range, a heat sink must be mounted on top of the "PENTIUM".
FIG. 2 is a cross-sectional view of CPU assembly 18 and mother board 17 of FIG. 1. Referring now to FIG. 2, a socket 40 is mechanically mounted and electrically connected to mother board 17. A packaged "PENTIUM" chip 42 is inserted into socket 40, and a heat sink 44 is mounted to the top of "PENTIUM" chip 42. Heat sink 44 consists of a base portion 46 and a portion in which grooves 47 have been formed so that fins 48 protrude from base portion. The fins are provided to increase the surface area of heat sink 44 and thereby increase its heat dissipation qualities.
An expansion board plugged into connector 21, 25 through can extend the entire length of mother board 10. This is because the components located in area 20 do not exceed the 0.6 inch specification. However, all previous "PENTIUM" heat sinks when combined with the height of socket 40 and "PENTIUM" package 42 exceed the clearance specification between the mother board and the closest edge of an expansion board at 0.6 inches. As a result full length extension boards cannot be used with sockets 22, 23 and 24.
Until recently, this problem was avoided by merely making half length expansion cards. However, the demand for more powerful expansion functions has steadily increased and with it the requirement to use full length expansion boards. To date this need has been met by attempting to add one or more additional full length expansion boards by modifying the heat sink as shown in FIG. 3a, b and c. Referring now to FIG. 3a, heat sink 50 has a portion 52 that is thin and the remaining fin portion 54 which are even higher than the fins in FIG. 2. In this configuration, there is sufficient clearance for one full length expansion board to fit over portion 52. In FIG. 3b, heat sink 54 has a thin portion 56 is in the middle with two fin portions 58 and 60. In FIG. 3c, heat sink 62 thin portions 64 and 66 on either side and a very high finned portion 68 in the middle. With this configuration, two additional full length expansion boards are possible.
All three attempts to make space for additional expansion boards cut away at the horizontal surface area of the fin area and compensated for this loss in surface area by increasing the height of the remaining fins.
While the approaches of the prior art work to provide at least some extra space for expansion boards, they all suffer from the deficiency that not all of the space over the top of the CPU can be used for full length expansion cards, and they provide poor cooling due to air blockage.